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Factpages Norwegian Offshore Directorate
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11.12.2024 - 01:27
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GASSUM FM

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  • General information

    General information
    Attribute Value
    Lithostrat. unit
    The lithostratigraphic unit's official name.
    GASSUM FM
    NPDID lithostrat. unit
    Norwegian Offshore Directorate's unique id for lithostratigraphic units.
    49
    Level
    Indicates the lithostratigraphic unit's level. Legal values: GROUP, FORMATION, MEMBER.
    FORMATION
    Lithostrat. unit, parent
    The parent lithostratigraphic unit's official name. See also level. Will be empty if Level = GROUP.
  • Level below

    Level below
    Lithostrat. unit
  • Description

    Gassum Formation

    Name
    After the village of Gassum, Jutland, Denmark, (Larsen, 1966).
    Well type section
    Danish well Gassum No. 1 from 1613 m to 1643 m below ground (Ground evelation 53.3 m) (Bertelsen, 1978).
    Well reference sections
    In Norwegian waters wells 17/10-1 (Shell) from2682 m to 2825 m, coord N 58°01 '54", E 03°09'58" (Fig 3.23) . and 7/9-1 (Conoco) from 2601 m to 2609 m, coord N 57°20' 37.1", E 02°51'21.4" (Fig 3.24) . The section in well 17/10-1 was included by Deegan and Scull (1977) in the Skagerrak Formation .
    Thickness
    In the Norwegian reference wells the thickness of the Gassum Formation is 143 m ( 17/10-1 ) and 8 m ( 7/9-1 ).
    Lithology
    In the type well the formation consists of predominantly light grey to whitish, in places rather coarse-grained sandstones, with subordinate dark-coloured clay bands and coal lenses (Larsen, 1966). In Norwegian waters the formation is predominantly a white to light grey, mainly fine to medium grained sandstone, but frequently contains coarse sand and gravel. It is often calcite cemented and in some instances contains glauconite.
    Boundaries
    In the Norwegian sector the lower boundary may be characterized by a general lowering of the velocity when entering the underlying Skagerrak Formation . Often this boundary coincides with a distinct horizon with high gamma ray response (e.g. well 17/4-1 (Elf) and well 9/12-1 (Shell)).
    The upper boundary of the Gassum Formation is easily picked where it is overlain by Lower Jurassic shales of the
    Fjerritslev Formation or Upper Jurassic shales of the Boknfjord or Tyne groups. Where the Gassum Formation is overlain by the Middle Jurassic Bryne Formation (Norwegian sector), the boundary may only show a slight decrease in the gamma ray response and an overall decrease in velocity marking the appearance of the Bryne Formation .
    In the reference well
    17/10-1 , where the Fjerritslev and Bryne formations are missing, the Gassum Formation is overlain by the shales of the Boknfjord Group .
    Distribution
    In the Norwegian sector the Gassum Formation occurs throughout the Norwegian-Danish Basin, on the Southern Vestland Arch and along the northeastern margin of the Central Graben. Its distribution towards the axial part of the Central Graben is unknown. It is often completely or partially eroded as a result of mid-Jurassic earth movements.
    Age
    Rhaetian in the type well, but seems to become younger northwards (Bertelsen, 1978). Sparse dating in the Norwegian sector gives Rhaetian to Sinemurian ages.
    Depositional environment
    The sedimentology of the Gassum Formation in the Norwegian sector has not been much studied, but is assumed to represent fluvial to marginal marine deposits laid down during a transgressive phase at the Triassic/Jurassic transition.
    Source
    • Vollset, J. and Doré, A. G. (eds.) 1984: A revised Triassic and Jurassic lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 3, 53 pp.
  • Wellbores penetrating

    Wellbores penetrating
    Wellbore name
    Wellbore completion date
    Top depth [m]
    Bottom depth [m]
    20.08.1978
    3575
    3604
    05.02.1969
    3275
    3334
    29.05.1971
    2601
    2609
    23.09.1976
    3554
    3676
    07.02.1972
    2680
    2704
    19.08.1971
    2082
    2121
    26.06.1976
    1524
    1539
    17.01.1971
    1494
    1567
    19.08.1969
    1860
    1900
    07.02.2011
    2800
    2988
    23.10.2021
    2455
    2466
    24.03.1969
    2682
    2825
    21.06.1972
    2410
    2446
    03.02.1980
    2617
    2638
  • Wellbores with cores

    Wellbores with cores
    Wellbore name
    Wellbore completion date
    Core length [m]
    23.09.1976
    18